By Jon Frandsen, Senior Editor February 13, 2008 This may be the closest, most interesting nomination battle the country has seen in decades, but it poses a real danger to the two Democratic candidates. While they slug it out, delegate by delegate, John McCain will be sharpening his claws on them, their positions and their weak spots. Plus, news coverage is likely to focus on the horse race far more than the individual candidates -- and while many Democrats will remain transfixed, what could be more soporific to the broader public than delegate counts, behind-the-scenes courting of super delegates and plotting strategy for credentials fights at the convention? To avoid becoming irrelevant or caricatured in the public mind by McCain, Obama and Clinton will have to move beyond the core image and message they have crafted. That poses problems for both of them. Obama is the rock star of the moment. He's won eight straight primaries, leads in pledged delegates and is eating into Clinton's base. But Obama's appealing theme of hope and unity could quickly grow stale and thin if he does not fill it out with details of just what it is he will unify Americans behind and where he will lead them. McCain made that vulnerability clear in his victory speech Tuesday night when he said: "To encourage a country with only rhetoric...is not a promise of hope. It is a platitude."Clinton has a more detailed platform and displays a greater mastery of policy on the stump. But her message of experience and toughness -- "I'm tested. I'm ready. Let's make it happen" -- also has the effect of reminding voters of how she was tested and of the partisan battles of the 1990s. She will have to find a way to keep voters firmly rooted in the future.Clinton and Obama have concentrated on their qualities and vision because there is really not much of a difference between them on policy. But they won't have that luxury for much longer. They need to outline a clearer image of what they would look like as a president facing a troubled world and how they will start changing things -- or else McCain will do it for them.